1. Field of the Invention
The present invention generally concerns (i) processes for making composite laminate materials from multiple sheets of thin metals; (ii) laminate composite materials so made; and (iii) uses of the laminate composite materials so made, particularly in lightweight armor.
The present invention particularly concerns (i) processes for making in air in a heated load press composite laminate materials at large size and low cost, including in contoured form; (ii) composite laminate materials having large numbers of (a) tough metal layers interleaved with (b) hard intermetallic regions; and (iii) the tailoring of hard composite laminate materials for use, among other applications, as lightweight vehicular and body hard armor.
2. Description of the Prior Art
2.1 Armor
The following discussion, and facts, are presently, circa 1998, available at many sites on the Internet. The following materials of this section 2.1 are in particular derived from information available, circa 1998, at the web site of Armor Technology Corporation, www.armortechnology.com.
2.1.1 Armor
Armor is a protective ‘skin’, or plating for protection of an underlying structure. There are basically three types of armor. Homogenous armor has the same hardness throughout. Face-hardened armor has an extremely hard outer layer while the rest is hard, but less brittle. Laminated armor is made up of several hard layers of material, such as steel, titanium, ceramics, etc.
Tanks and other military vehicles use abundant armor. Armor is also used in armored land combat vehicles, structural shields, load bearing security walls, armored cars and other commercial vehicles, high speed trains, cash carrying vehicles (especially as all-around protection); private cars (most usually in door and floor panels); financial institutions particularly in security doors, partitions and briefcases; private homes particularly in front doors, walls and partitions; helicopters and light aircraft particularly in seats, doors, panels, channels; and boats and small ships particularly in superstructures, cabins and control rooms.
Composite armors are efficient structural materials that also provide outstanding protection against ballistic projectiles. They were originally developed for military armored vehicles to eliminate the need for parasitic armor.
2.1.1. Background of Body Armor
The rationale for body armor is well established. As well as its obvious application in warfare, every year about 60 sworn police officers are shot to death in the United States in the line of duty. At the same time, about 20 are saved by wearing armor. Had all the officers shot in recent years been wearing armor when shot, another 15 per year would likely have been saved from fatal gunshot wounds, roughly doubling the present number saved, and more than 15 others would likely have been saved from death by other causes.
Most police officers serving large jurisdictions report they have armor and wear it at all times when on duty and clearly identifiable as police officers. The kind of armor usually worn is soft armor, which is designed to be concealable—most styles are undergarments—and comfortable enough to be worn routinely. Such armor is designed for protection from handgun bullets but not from rifle bullets or edged or pointed weapons such as knives or icepicks. The distinctive, nonconcealable “tactical” armor worn by police SWAT (Special Weapons and Tactics) teams for protection from rifle bullets as well as pistol bullets is more familiar to many laymen. This latter type of “hard” personal armor is the type of armor supported by the advanced materials of the present invention, which are very lightweight but rigid.
Lightweight, composite, body armor preferably protects effectively against not only most known small-arms, as at present, but also against high velocity ballistic threats. Optional plate inserts presently provide some extra level of protection against rifle bullets, but are not presently of practical size and weight for extended wear.
A comfortable, ergonomic, body armor product would preferably accord the wearer maximum comfort even during prolonged periods of wear. At least front and back protection should be provided. The armor garment would desirably not contribute to heat stress of the wearer, but would readily accommodate physical effort by the wearer.
2.1.2 Summary of NIJ Standard 0101.03
The National Institute of Justice (NIJ) standard 0101.03 is of relevance to the present invention because, as will be explained, the materials of the invention are readily used in construction of, among diverse other forms of armor, “hard” body armor. The body armor so constructed, although lightweight at about 3.0 to 4.5 grams per cubic centimeter, is potentially capable of meeting NIJ standard 0101.03 type IV, as explained below. It is the first practical body armor of both such (i) thinness and (ii) light weight known to the inventors to potentially so meet this standard. For example, it will be found in this specification disclosure that the 0.2 inch thickness of the new material has reliably stopped high-power penetrating rounds (of the types explained below) that will penetrate ¾″ of hard steel armor, which steel armor is, of course, also much more dense.
The National Institute of Justice (NIJ) standard 0101.03 is a performance standard, not a construction standard. It does not specify the area of coverage, nor does it specify any material to be used in the armor. The standard is thus directed to permitting and encouraging technical innovation, including the development of materials and designs providing better ballistic resistance, greater comfort, or lower cost. However, some aspects of the standard were introduced specifically to provide stringent tests of likely weak points of Kevlar fabric armor, which at the time was almost the only type of concealable body armor marketed in the United States.
NIJ notes that “For the purposes of the . . . body armor certification procedures, the following definitions have been adopted:
A body armor MODEL is a manufacturer designation that identifies a unique ballastic panel construction; i.e., a specific number of layers of one or more types of ballistic fabric and or ballistic-resistant material assembled in a specific manner.
A body armor STYLE is a manufacturer designation (number, name, or other descriptive caption) used to distinguish between different configurations of a body armor product line each of which includes the same model of ballistic panel.
The 0.03 standard defines six standard types of ballistic resistance for which armor may be tested and provides for custom testing for “special type” ballistic resistance. Each type is defined in terms of the type or types of bullets fired at panels of the armor to test its ballistic resistance (see table 1, following). Two types of handgun bullets are fired to test for Type I, II-A, II, or III-A ballistic resistance, which soft armor can provide. One type of rifle bullet is fired to test for Type III or IV ballistic resistance, which hard armor can provide.
Each standard type of armor is expected to offer protection against the threat associated with it as well as against the threats associated with all other standard types of armor appearing above it in table 1. For this reason, the types of armor defined by NIJ Std.-0101.03 are often referred to as “levels,” level II-A being presumably superior to level I, for example. However, a certification test for type II-A ballistic resistance would not actually test resistance to type I threats. In addition, an NIJ guide specifies other threats against which it expects armor of each standard ballistic-resistance level to provide protection (see table 2), even though the 0.03 test does not actually test resistance to such threats.
TABLE 1Types of Ballistic Resistance Defined by NIJ Standard0101.03 in Terms of Bullets and Velocities Specified for TestingBulletImpactmassvelocity1TypeBullet caliber and type(grams)(ft/s)I.22 long rifle high-velocity401,050.38 round-nose lead158850II-A.357 jacketed soft-point1581,2509-mm full metal jacket1241,090II.357 jacketed soft-point1581,3959-mm full metal jacket1241,175III-A.44 magnum lead semi-2401,400wad cutter gas-checked9-mm full metal jacket1241,400III7.62 mm full metal jacket1502,750IV.30–06 armor-piercing1662,850Specialcustomcustomcustom1Minimum velocity; the maximum velocity for a fair hit is 50 ft/s greater.SOURCE: National Institute of Justice, 1987.
TABLE 2Types of Ballistic Resistance Defined by NIJ Standard0101.03 in Terms of Guns and Ammunition Against Which Protection isExpectedTypeThreatI.22, .25, and .32 caliber handguns,.38 Special lead round-noseII-A.38 Special high-velocity, .45's, low-velocity.357 Magnum & 9-mm, .22 riflesIIHigher velocity .357 Magnum and 9-mmIII-A.44 Magnum and submachine gun 9-mmIIIHigh-power rifle:5.56 mm, 7.62 mm FMJ, .30 carbine,.30–06 pointed soft point,12-gauge rifled slugIVArmor-piercing rifle bullet, .30 caliber(1 shot only).SOURCE: National Institute of Justice, 1987 [144] and 1989 [145].
The NIJ standard specifies that “Four complete armors, selected at random and sized to fit a 117 cm (46 in) to 122 cm (48 in) chest circumference, shall constitute a test sample. (Note: The larger the size, the more likelihood that all ballistic testing will fit on just two complete armors.) In quality assurance, “selected at random” usually means “selected at random with uniform probability”—i.e., sampling should ensure that all units of the model should have the same chance of being selected to be tested. However, this is impossible if samples are selected for certification testing before production of the model has been discontinued. Typically samples are selected after only a few units have been produced; consequently, the sampling procedure does not guarantee that the samples are representative of yet-to-be-produced units of the model, particularly of smaller sizes.
Armor to be tested is mounted on a flat block of inelastic backing material—typically modeling clay—to be shot. The impact velocity of each bullet is measured using a ballistic chronograph. If the bullet hits an appropriate point on the panel at an impact velocity within specified limits (see table 1), then the impact is considered a fair hit. The test requires a fair hit in each of six specified areas on each panel in a specified sequence (see the diagrammatic representation in the next following paragraph). Each shot must impact at least 3 inches from the edge of the panel and at least 2 inches from the closest point of impact of any prior shot.
The sequence of aim points on each panel, as specified in NIJ Standard 0101.03, looks like the following diagrammatic representation.
* #1#4** #6* #5#2** #3All shots must be at least 7.6 cm (3 in) from any edge and at least 5 cm (2 in) from another shot. The source for this information is the National Institute of Justice, 1987.
In tests of Type I, II-A, II, or III-A ballistic resistance, four complete armors, typically including eight armor panels (four each front and back) are usually shot. Each ballistic element (front or back panel) is sprayed with water and then shot with test bullets of the first type, then another one is sprayed and shot with test bullets of the second type. This is repeated with un-sprayed, dry samples. This requires a minimum of 48 shots per test: 2 element types (front and back) ×6 shots each ×2 types of bullets ×2 wetness conditions.
If the velocity of a shot is too low and it does not penetrate the panel, or if the velocity of a shot is too high and it does penetrate the panel, then the shot is repeated, aimed at least 2 inches from the closest point of impact of any prior shot. However, in more than eight shots (of one caliber) may be fired at any panel. The armor cannot be certified if any fair shot penetrates.
After the first fair shot at each panel, the panel is removed from the backing and the depth of the crater (called the backface signature or BFS) is measured. If the BFS exceeds 44 mm or if the armor was penetrated, it fails; if not, the panel is replaced on the backing without filling the crater or otherwise reconditioning the backing material, and testing for penetration is resumed. (10) The standard prohibits adjusting the panel (e.g., patting it down) thereafter, unless it is reused for testing with a second type of bullet.
2.2 Specific Previous Materials
Certain previous materials relevant to the present invention are discussed in the following sections. The section headings are for convenience only, and the materials described within the section may be relevant to the present invention in any of the manner of fabrication, the existence of intermetallic regions, the particular metals used and/or compounded, and/or other factors not clearly delimited in the section headings. A greater appreciation of the diverse, but generally remote, relevance of the following reference to the present invention may potentially be gained if the present invention is first understood, and the following references and previous materials only then considered (reconsidered).
2.2.1 Aluminum, Titanium, and Steel; and Aluminum, Titanium, Titanium-Aluminum or Steel Intermetallics
The present invention will be found to concern a hard intermetallic compound preferably having as one of its constituent components aluminum. If is known in metallurgy that intermetallic compounds of aluminum, a relatively soft metal, can be hard.
There are many ways to derive intermetallic compounds. For example, U.S. Pat. No. 5,098,469 to Rezhets issued Mar. 24, 1992 for a POWDER METAL PROCESS FOR PRODUCING MULTIPHASE NI—AL—TI INTERMETALLIC ALLOYS and assigned to General Motors Corporation (Detroit, Mich.) concerns a powder metallurgy process for producing near-net shape, near-theoretical density structures of multiphase nickel, aluminum and/or titanium intermetallic alloys. The process employs pressureless sintering techniques, and consists of blending a brittle aluminide master alloy powder with ductile nickel powder, so as to achieve the desired composition. Then, after cold compaction of the powdered mixture, the compact is liquid phase sintered. The four-step liquid phase sintering process is intended to ensure maximum degassing, eliminate surface nickel oxide, homogenize the alloy, and complete densification of the alloy by liquid phase sintering.
The intermetallic compound, and regions, of the composite laminate material of the present invention will be seen to be produced from foils, or thin sheets, of different metals. U.S. Pat. No. 5,256,202 to Hanamura, et. al. issued Oct. 26, 1993 for a Ti—Al INTERMETALLIC COMPOUND SHEET AND METHOD OF PRODUCING SAME assigned TO NIPPON STEEL CORPORATION (Tokyo, JP) concerns a Ti—Al intermetallic compound sheet of a thickness in the range of 0.25 to 2.5 mm formed of a Ti—Al intermetallic compound of 40 to 53 atomic percent of Ti, 0.1 to 3 atomic percent of at least one of material selected from the group consisting of Cr, Mn, V and Fe, and the balance of Al, and a Ti—Al intermetallic compound sheet producing method comprising the steps of pouring a molten Ti—Al intermetallic compound of the foregoing composition into the mold of a twin drum continuous casting machine, casting and rapidly solidifying the molten Ti—Al intermetallic compound to produce a thin cast plate of a thickness in the range of 0.25 to 2.5 mm and, when necessary, subjecting the thin cast plate to annealing and HIP treating. The Ti—Al intermetallic compound sheet is stated to have excellent mechanical and surface properties.
2.2.2. Layered Armor
The composite material of the present invention, suitable for use as armor, will be seen to have regions, or layers (albeit without sharp boundaries) of differing materials. It has been known since ancient times to make armor in layers where each layer imparts some particular quality to the armor. Most recently the incorporation of hard ceramics in armor has been much pursued.
An exemplary United States Patent is U.S. Pat. No. 4,836,084 to Vogelesang, et. al. Jun. 6, 1989 for ARMOR PLATE COMPOSITE WITH CERAMIC IMPACT LAYER. This patent concerns an armor plate composite composed of four main components, viz. the ceramic impact layer, the sub-layer laminate, the supporting element and the backing layer. The ceramic impact layer is asserted to be excellently suitable for blunting the tip of a projectile. The sub-layer laminate of metal sheets alternating with fabrics impregnated with a viscoelastic synthetic material is perfectly suitable to absorb the kinetic energy of the projectile by plastic deformation, sufficient allowance for said plastic deformation being provided by the supporting honeycomb shaped layer. The backing layer away from the impact side and consisting of a pack of impregnated fabrics still offers additional protection. The optimum combination of said four main components is said to give a high degree of protection of the resulting armor plate at a limited weight per unit of surface area.
There is also present interest in putting high-strength fibers into composite materials suitable for armor. U.S. Pat. No. 5,635,288 to Park issued Jun. 3, 1997, for a BALLASTIC RESISTANT COMPOSITE FOR HARD-ARMOR APPLICATION concerns a ballistic resistant composite for hard-armor application. The composite includes a rigid plate, and a ballistic laminate structure supported by the plate. The laminate structure includes first and second arrays of high performance, unidirectionally-oriented fiber bundles. The second array of high performance, unidirectionally-oriented fiber bundles is cross-plied at an angle with respect to the first array of fiber bundles, and is laminated to the first array of fiber bundles in the absence of adhesives or bonding agents. First and second polymeric films are bonded to outer surfaces of the laminated first and second arrays of unidirectional fiber bundles without penetration of the films into the fiber bundles or through the laminate from one side to the other. Thus, a sufficient amount of film resides between the laminated first and second arrays of unidirectional fiber bundles to adhere the first and second arrays of fiber bundles together to form the ballistic laminate structure.
A combination of both the concepts of (i) intermetallic phase regions, and (ii) layers is shown in U.S. Pat. No. 4,853,294 to Everett, et. al. issued Aug. 1, 1989 for CARBON FIBER REINFORCED METAL MATRIX COMPOSITES and assigned to United States of America as represented by the Secretary of the Navy (Washington, D.C.). This patent concerns an improved metal, alloy, or intermetallic matrix composite containing carbon reinforcing fibers. The carbon reinforcing fibers are protected from interaction with the matrix material by an inner and an outer barrier layer. The outer layer is any one of the group of stable, non-reactive ceramic materials used to protect fibers, and the inner layer is a ductile, low density, oxygen desorbing rare earth metal. The carbon fibers are particularly useful in forming composites with a titanium aluminide matrix.
2.3 Why Hard Armor Fails
The failure of hard armor, and its penetration by projectiles, is enhanced when the speed of sound in the hard material of the armor is greater than the speed of the penetrating projectile, as is most often the case. Cracks propagate in the armor at the speed of sound (in the material of the armor), fragmentation occurs, and fragments are displaced from in front of the projectile before complete, energy-absorbing, deformation of these fragments by the projectile has occurred.
For example, the hardness of ceramic is unexcelled (save by diamond, and other rare materials not presently practical for armor). It is generally accepted that the ability of ceramic armor to defeat penetration by a projectile can be enhanced if the armor is confined—i.e., kept in place during impact—in order to limit fragmentation and fragment dispersion. However, in real ballistic events providing such confinement to ceramics is difficult and expensive to achieve.
The present invention will be immediately next seen to concern a material—a composite laminate material produced by a new, but simple, process—where a hard, ceramic-like, component is “kept in place” even during attempted penetration of the material by a high-speed projectile. Moreover, the flight of a projectile attempting penetration is significantly “interfered with”, both in direction and in the orientation of the projectile, by the new material to the detriment of penetration of the material by the projectile.